1 files changed, 40 insertions, 0 deletions
diff --git a/src/2017/day3/aoc.cpp b/src/2017/day3/aoc.cpp
index ed2d9d3..85c2aa4 100644
--- a/src/2017/day3/aoc.cpp
+++ b/src/2017/day3/aoc.cpp
@@ -1,5 +1,45 @@
 #include "aoc.h"
+#include <math.h>
 
 namespace aoc2017 {
 
+std::pair<int, int> circle(int t) {
+  int i = 1;
+  int j = 0;
+  while ((i * i) < t) {
+    i += 2;
+    j += 1;
+  }
+  return {j, i};
 }
+
+void middles(int i, int m[]) {
+  int x = i * i;
+  for (int a : {0, 1, 2, 3}) {
+    int n = x - i + 1;
+    m[a] = (n + x) / 2;
+    x = n;
+  }
+}
+
+int closest(int t, int m[]) {
+  int min{INT32_MAX};
+  for (int a : {0, 1, 2, 3}) {
+    int d = std::abs(t - m[a]);
+    if (d < min) {
+      min = d;
+    }
+  }
+  return min;
+}
+
+int day3(int target) {
+  auto p = circle(target);
+  int ms[4] = {0};
+  middles(p.second, ms);
+  // printf("%d -> %d %d %d %d\n", target, ms[0], ms[1], ms[2], ms[3]);
+  int d = closest(target, ms);
+  return d + p.first;
+}
+
+} // namespace aoc2017